It is known to prepare magnetizable beads (U.S. Pat. No. 4,339,337) ranging in diameter from 0.05 to 3 mm by the suspension polymerization of a vinylaromatic monomer in the presence of an organosoluble initiator, a suspending agent and a magnetizable charge which is dispersed in a solution of a non-water-soluble polymer in the monomer. The beads obtained contain magnetizable charges distributed in the polymer matrix.
It has also been proposed (U.S. Pat. No. 4,358,388) to prepare latices of magnetizable hydrophobic polymers by the homogenization of an aqueous solution of emulsifier and a dispersion of a magnetizable charge in an organic phase composed of an organosoluble initiator, all or part of the hydrophobic monomer and/or a water-insoluble organic compound, followed by polymerization. The latices obtained are composed of polymer particles approximately 0.03 to 5 .mu.m in diameter containing magnetizable charges distributed in the polymer matrix, the charges tending to migrate to the periphery.